11-10-2018 9:35 AM
A bid can only be retracted by a buyer if the auction is live.
What you've encountered is called a chargeback - when the card holder reports the payment as being unauthorised by them, either because somebody has stolen their card or their account has been accessed or because they're pulling a fast one.
PayPal Seller Protection covers you against a chargeback if you have your proof of posting slip showing that you sent the item out to the address that Paypal told you to send it to. Make sure than scan or photograph this and that PayPal have a copy if it a.s.a.p.